When a salmon-colored rash flared on my 3-year-old son’s tummy one afternoon in August, I shrugged it off. The next time I asked Evan to lift up his shirt to take a photo, it was gone. When he stopped sleeping through the night, I thought it was a dreadful new developmental phase. But then on a Saturday, he stopped walking and spiked a 104-degree fever. A nurse gave me clear directions: “Get in your car, and start driving to the ER.”